When judging a new place, a traveler must first always reckon with his or her point of departure. Arriving in Calcutta by bus from Dhaka, the capital of next-door Bangladesh, is like arriving in West Berlin from East Berlin during the Cold War—a trip I made several times. Grayness is left behind. Instead of the rusted signs of Dhaka, giant, swanky billboards advertising global products glow in the night like back-lit computer screens. Traffic is dominated in Dhaka by creaky old bicycle rickshaws; in Calcutta, by late-model cars. There are, too, the sturdy yellow Ambassador taxis, zippy little Indian-produced Marutis loaded with families, and many luxury vehicles.

Yet the rickshaws that you also see in Calcutta provide a signature image of exploitation worse than almost anything you’ll see in Dhaka: one human being is transported by another, who is not merely furiously pedaling uphill, but actually running uphill on his bare feet, pulling the rickshaw like an animal.

Calcutta is, frankly, obscene. I walked out of a tony espresso bar—its windows cluttered with credit-card stickers—that offered an eclectic Indian-cum-cosmopolitan cuisine of extravagant mocha cocktails and paneer-tikka sandwiches. As I left the air-conditioning for the broiling street, I was careful not to stumble over families sleeping on cardboard along a sidewalk where men and women urinated. It was here that a young man began to follow me. After several blocks, I still couldn’t shake him. He thrust his résumé as a documentary film producer in my face and pleaded with me to hire him. “I realize I am invading your privacy, sir,” he said. “But what am I to do? Perhaps you are angry with me. I will stop bothering you, but only if you give me a job.” He was dressed poorly but neatly, out to make an impression. In the United States, junk-mail offers and telemarketing calls at least allow you the luxury of tearing up the piece of paper or hanging up the phone. In Calcutta, such unwanted entreaties take a very personal form. Street solicitations here are a form of cold-calling. Escape is impossible.

Calcutta’s invasive poverty stopped hippies in their tracks. The hippie trail across Asia in the 1960s and ’70s followed the Ganges east to the holy Hindu city of Varanasi, then veered north to Kathmandu, Nepal, rather than continuing on to Calcutta. “On first acquaintance,” Geoffrey Moorhouse writes in Calcutta: The City Revealed (1971), the city “is enough to destroy any romantic illusions about gentleness and brotherly love.”

The slums may be worse in Mumbai (more than four times as many people live in them), but the slums there are more segregated from the wealthier areas; in Calcutta, beggars and street people spread throughout the city, making it much harder to avoid the poor. And like Mumbai, Calcutta has a population density that is among the world’s highest.

The first week of the summer monsoon—smothering heat followed by pounding rain—is the best time to experience Calcutta’s two separate and unequal universes: the world with air-conditioning, and the one without. The first is that of an upwardly mobile, international civilization; the second constitutes the miserable reality of the street, where 1.5 million poor Calcuttans live within a few feet of air-conditioning, even as they will never experience it. The door to this espresso bar, or to that charming bookshop with those Penguin paperbacks, represents a border as hard to cross as any drawn on a map.

In north Calcutta, the pavement is taken up by long stretches of tarpaulin-and-burlap lean-tos, inside which families live, with older siblings watching younger ones while the women work as maids and the men as construction workers. But as wrenching as the scene appears, if you wade through the street people, past this partially opened door, or under that chain, you will find another Calcutta: a maze of beautiful and derelict 18th- and 19th-century mansions, built by former rajas and merchants, with blackened, weather-stained walls; intricate brickwork in Muslim, Hindu, and neoclassical styles; and colonnaded courtyards strangled by vines and other greenery. The most impressive of these is the Marble Palace, whose lightless rooms are crowded with dusty Belgian mirrors, classical statuary, Chinese vases, hookahs, crystal glass chandeliers, lithographs, and four paintings by Rubens. Like this rambling palace, Calcutta is an eccentric jumble, of which poverty is but the outer layer.

RUNNING OUT OF TIME: New laws are forcing rickshaws off Kolkata's streets.

Despite the distracting horror of pavement life, the real story of Calcutta is its transformation into a global city, with expatriates returning to invest in malls and restaurants, in the process enforcing the standards of service they learned in the West. Early this year, a 900,000-square-foot mall opened in the southern part of the city; among the largest in India, it’s one of 40 new retail centers set to open in Greater Calcutta by 2011. This is in addition to 20 new multiplex cinemas arising as the city expands to the east. Then there are the luxury condominiums going up, with names like Highland Park and Silver Spring. “If you think of the British Empire as the first go at globalization,” explained Santosh Ghosh, an urban planner, “then Calcutta, as the capital of British India, with its museums and botanical gardens, was a global city when Singapore and Kuala Lumpur were still villages. Now Calcutta is finally catching up.”

The spirit of globalization fuels the gusto with which this Hindu-Muslim city celebrates Christmas—another British legacy—with colored lights festooning the streets, decorations on sale everywhere, and life-size Santa Clauses sculpted of mud and straw in the same workshops that produce the myriad Hindu gods. On Christmas Eve, thousands of Calcuttans of different religions converge on St. Paul’s, the British-built 19th-century Gothic cathedral, infusing the holiday with a cosmopolitan ambience.

The pace of change in Calcutta still isn’t on a par with that of China, but the city is headed in the same direction. Shikha Mukerjee, who directs a nongovernmental organization and has spent her whole life in Calcutta, notes that the world of the leisurely wealthy, with their live-in servants, is disappearing, as the upper classes live a less secure, more frantic existence. But Calcutta’s middle class, which has always been here, has taken on greater visibility, thanks in part to its consumerist buying sprees. According to a recent study by McKinsey & Company, discretionary spending by Indian consumers accounted for 52 percent of average household consumption in 2005 (up from 39 percent in 1995); by 2025, it will rise to 70 percent.

“It’s not the fancy malls,” Mukerjee said, “but the low-end centers that are the heart of the change—the people who have created jobs for themselves by altering clothes, fixing appliances, and so on. I have a tailor who travels from an outlying slum area each day to occupy a particular place on the sidewalk with his sewing machine, where his clients come to him. He’s saving money, he told me. That’s what Calcutta is really about these days.” The pavement soup kitchens selling noodles and curry dishes testify to the rise of a lower middle class, up from abject poverty, that requires cheap meals during the workday. The increase in family cars has led to the most-persistent traffic jams I have experienced in the developing world, worse even than Tehran’s, Bangkok’s, or Cairo’s.